If LG is using a Sony camera sensor in the Nexus 4, it's entirely possible that they're using a different radio chip than usual too. It's all about supplies and what's affordable and what's available.
IE: one reason to use a different part in the Nexus 4 than their own flagship phones is because they wouldn't have enough of part X left over after using them in the flagship phones to have enough left for the Nexus 4. So they go with a part from a different manufacturer so that they can produce enough of all their phones at a steady rate without worrying about part shortages. Another reason would be to cut costs if the difference in performance is negligible.